Initial installation and subsequent repair of electrical cables require the splicing together of cables. Cables comprise electrical conductors surrounded by a protective sheath. The sheath and conductors may be encased within a protective conduit. "Sheath" and "conduit" are used herein interchangeably.
The severed ends of cables are prepared for splicing by careful removal of portions of the cable sheath. It is important to cut the sheath to the correct depth. If too deep a cut is made, the insulation or the conductors beneath the sheath may be damaged.
Installed cables are usually concealed in cramped spaces such as trenches, lock boxes, pedestals and the inside of walls or ceilings. In order to gain access to cables in such spaces, a large area around the cables must be cleared. Considerable excavation or destruction around the cutting area can compromise the structural integrity of the surrounding area and increase the cost of repairs.
Various tools have been provided for cutting strand-encircling sheaths. Conventionally, a hand-held knife can be employed. In use, a technician holds a cable in one hand and wields a knife in the other hand. However, a technician's hands are unable to provide a stable support for the cable and do not allow for accurate measurement of the depth of penetration of the knife blade. Due to these disadvantages, damage to the underlying insulation and conductors is likely. In addition, the exposed knife blade is potentially dangerous to the technician.
A type of sheath cutting tool especially intended for the purpose is described in U.S. Pat. No. 5,074,043 to Mills. U.S. Pat. No. 5,074,043 discloses a tool including a tubular housing, a blade assembly and a means for positioning the blade. The blade assembly includes a blade held within a carrier comprising two plates on opposite sides of the blade, each plate having a recess to expose a portion of the blade edge. The blade assembly is held in and against a slot in the housing by a tension spring which surrounds the circumference of the housing. In operation, a cable is positioned within the housing and the tool is manually rotated to circumferentially cut the cable sheath.
The penetration of the blade into the cable sheath is limited to the portion of the blade exposed at the central recess portion of the blade carrier. In addition, since the depth of the blade cannot be adjusted, the tool cannot accommodate cables having different diameters.
Other types of tools include those described in U.S. Pat. No. 4,955,137 to Matthews, U.S. Pat. No. 4,799,406 to Diaz-De-Guerenu-Aguirrebeitia and U.S. Pat. No. 3,826,001 to Bilbrey et al. These patents disclose means for supporting a cable and means for cutting the cable sheath. The cutting means include cutting members secured to threaded shafts. The threaded shafts are rotated to adjust the penetration depth of the cutting member.
Still additional types of tools include those disclosed in U.S. Pat. No. 4,805,302 to Steiner and U.S. Pat. No. 4,366,619 to Bieganski. These tools disclose a housing having an opening for a cable and a sliding frame mounted within the housing. The cutting member is mounted on the sliding frame. The sliding frame, and thus the cutting member, are biased into the cable opening by a spring within the housing. In operation, the cutting member is positioned out of the cable opening and a cable is inserted therein. The cutting member is then positioned in the cable opening, by releasing the sliding frame, and the tool is manually rotated to produce a circumferential cut on the cable sheath.
In U.S. Pat. No. 4,805,302, the depth of penetration of the cutting member is determined by a flange on the sliding frame which acts as a stop. In U.S. Pat. No. 4,366,619, the cutting member is additionally connected to a threaded shaft. Adjustment of the threaded shaft adjusts the depth of penetration of the cutting member.
None of the aforementioned tools are adapted for use on installed cable which does not have a readily accessible free end. Furthermore, the tools discussed above do not disclose a blade assembly including a blade setting means which acts in conjunction with a blade returning means.